Murder by the Glass (The Verity Long Mysteries)

Merlot-loving researcher Verity Long is happily sipping her way through a wine tasting weekend with her crime-writer boss happily, that is, until a fellow guest is murdered in the winery.
When a storm isolates them and brings down power and phone lines, Verity forgets bouquets, acidity, and floral top notes to concentrate on catching a killer.

Unable to contact the police, and with no internet for researching her suspects' motives or backgrounds, the amateur sleuth will need to sniff out the killer before there's another murder her own.